Apparatus and methods for control of waste treatment processes

ABSTRACT

Waste-treatment processes are enhanced through generation and introduction of specific biological populations customized to perform or favor specific tasks either during the main process, for the formation or precipitation of certain biological nutrients, or to accomplish solids formation reduction in a post-treatment process. These bacteria may be grown from specialized mixes of activated sludge and waste influent by exposing these materials to controlled environments (e.g., in an off-line treatment area). They may then be returned to the main process to perform certain tasks such as converting particulate cBOD into soluble cBOD for utilization, to reduce high solids yield organisms by supplementing the population characteristics with low yield organism characteristics, to provide biological nutrients or oxygenation assistance, to improve nitrification/denitrification efficiency, or to disfavor filamentous biology such as  Norcardia  sp.

RELATED APPLICATIONS

This application is a continuation-in-part of U.S. Ser. No. 10/985,265,filed on Nov. 10, 2004, which is a continuation of U.S. Ser. No.10/658,575, filed on Sep. 9, 2003 (now U.S. Pat. No. 6,833,074), whichis a continuation of U.S. Ser. No. 09/798,313, filed on Mar. 2, 2001(now U.S. Pat. No. 6,660,163). The entire disclosures of theseapplications are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to biological treatment of contaminatedliquids and effluent, and, more particularly, to methods and apparatusfor the creation and/or application of customized biology populations tobiological processes, such as wastewater treatment.

2. Description of the Related Art

Before being discharged to the environment, contaminated waters frommunicipal, commercial, and industrial sources frequently must be treatedto prevent harmful impacts. The treatment processes used are numerousand varied. A rudimentary conventional process is shown in FIG. 1. Thetreatment process often begins with a coarse removal step 110, in whichthe waste influent is typically treated by screening and grit removalprocesses. In some treatment processes, the coarse removal step 110 isfollowed by a surge tank or lagoon, sometimes known as an equalizationtank or a flow equalization vessel (not shown), to provide hydraulicinventory and reduce flow surges through the treatment process. Thecoarse removal step 110 can be then followed by the removal of sludgeand solids in a primary clarifier 112. Frequently the sludge from theprimary clarifier 112 is partially consumed in a digester 114, whichrecycles clear effluent back to the start of the process and diverts theunconsumed sludge to disposal.

In some processes the clear effluent overflow from the primary clarifier112 is stored in a flow equalization vessel (not shown). Such a vesselis used to provide inventory and to reduce flow surges through thetreatment process. This clear effluent overflow from the clarifier maybe mixed with activated sludge and aerated in an aeration unit 118before being fed to a secondary clarifier 120 for secondary treatment.In some processes the aeration unit 118 has insufficient capacity toprovide sufficient oxygen to meet the biological metabolism requirementsof the microorganisms present in the waste stream. Such processes wouldbenefit from additional oxygenation capacity.

The clear effluent overflowing the secondary clarifier 120 may bedisinfected by a disinfecting unit 122, which may apply, for example,chlorine or UV light, and discharged to a local waterway as effluent.The solids from the secondary clarifier 120 are generally thickened,e.g., by a filter press 124 and then sent off for disposal.

Biological processes are commonly used for the elimination ofcontaminants in the secondary treatment portion of the process, and maytake many forms. They generally involve exposure of the waste stream toone or more forms of microorganisms that stabilize or digest variouscontaminants. The microorganisms to be favored by the particulartreatment process implemented are chosen to complement the waste streamin terms of content, strength, the biochemical and chemical environmentused for treatment, and the specific effluent requirements. For example,the activated sludge process utilizes aerobic bacteria that remove thesoluble biological oxygen demand (BOD) from wastewater. Practice of thisprocess generally involves conducting wastewater into an aeration basincontaining a suspension of digestive microorganisms, thereby forming a“mixed liquor” that is aerated to furnish oxygen for consumption of theBOD, the formation of new biomass, and the respiration of biomassmaintained in inventory; the biomass sorbs, assimilates and metabolizesthe BOD of the wastewater. After a suitable period of aeration, themixed liquor is introduced into the secondary clarifier, in which thebiomass settles, allowing the treated wastewater to overflow into anoutlet effluent stream. All or a portion of the biomass separated fromthe effluent in 120 is returned to 118 to treat additional influent.

The BOD provided by the waste acts as “food” for the microorganisms. TheBOD may be measured and reported as total BOD that includes bothnitrogenous (NBOD) and carbonaceous oxygen demand (cBOD) or separatelyas NBOD and cBOD. This BOD, especially the cBOD, may be present inparticulate or soluble form. The propensity of a given organism tometabolize a particular form of NBOD or cBOD and the rate at which thisis done are determined by both the local environmental conditions andthe number of organisms of similar type. In addition to carbonaceous“food,” microorganisms require certain macronutrients for survival, suchas sodium, calcium, phosphorus, and/or nitrogen, and trace levels ofmicronutrients such as iron, sulfur, and/or manganese.

Controlled and efficient inclusion and removal of these macro andmicronutrients with the waste stream are managed within the treatmentprocess, and may be an important component of its operation with respectto meeting local effluent disposal requirements. Indeed, nutrientsrequired for efficient operation of the treatment process may alsocontribute to environmental discharge concerns. For example, althoughcertain microorganisms require phosphorus to survive, an excess ofphosphorus in the treated waste stream can mandate addition of chemicalsto precipitate and then coagulate and flocculate these materials topromote their separation and settling from the effluent to bedischarged, whereupon the resulting sludge is commonly disposed of in alandfill.

As these various materials are metabolized by the microorganisms theymay reproduce, and the degradable portions of the influent are convertedinto gases and excess biology. The excess biology may consist of liveand/or expired microorganisms and other organic materials, and willgenerally be disposed of as sludge at the terminal portion of theprocess. The clear effluent that remains is generally discharged to alocal receiving water body.

The microorganisms selected for the elimination of the contaminants inthe incoming waste stream may come from many sources. Most wastetreatment processes treat their incoming waste with recycled biologypopulations obtained from a downstream portion of the process. Recyclingof these microorganisms is convenient and inexpensive, but unfortunatelydoes not readily lend itself to the customized matching or tailoring ofa given biological population to the varying needs of the influent wastestream. The composition, effectiveness, and amounts of the variousrecycled populations of microorganisms are also affected by the feedcomposition present when they were generated, so they are especiallyimpacted by changes in the flow compositions or influent concentrations.These problems are exacerbated by the limited amount of flexibility mosttreatment plants have in manipulating the factors that favor a desiredbiological population profile. The options frequently are limited to thewasting of a portion of the sludge or some of its associated waterchemistry, in an attempt to drive the biological selection process to aparticular population balance by controlling the average “age” of thepopulation, balancing the slower growing, more efficient organisms withthe faster growing, more responsive organisms.

Partially in response to this need for varied populations, in responseto local effluent requirements, and in an effort to accelerate thetreatment process, a waste treatment plant may treat the waste streamwith a combination of biological environments generally within thesecondary treatment portion of the process. While virtually alltreatment schemes utilize several major classes of bacteria, includingobligate aerobes, facultative aerobes, nitrifiers, obligate anaerobes,and facultative anaerobes, manipulation of the different environmentswithin the particular scheme favor different classes of bacteria thatcompete with each other in the course of the treatment process. Theresults of this competition affect the efficiency of the treatmentprocess and the degree of treatment achieved in the final effluent.

Common to all of these processes, however, is generation of a wastestream of excess biology, generated because new growth exceeds death anddecay. In most instances that waste stream also will containparticulate, seemingly non-degradable organic and inorganic material, inaddition to the excess biology. Usually, the waste stream is removed asa portion of a solids recycle stream and it is directed to a terminalsolids treatment process, thus minimizing the volume of excess wastesolids that must be disposed of. The terminal treatment processfunctions primarily to concentrate and stabilize these materials fordisposal and may include further biological treatment (“digestion”) thatspecifically enhances general death and decay of biomass.

Both as described and as generally practiced, the current wastetreatment processes exhibit significant limitations. Conventional modesof operation do not allow microorganism populations to be tailored tothe characteristics of a particular waste stream, which may change overtime. Moreover, methods of controlling the microorganisms to provideenhanced quantities of desirable nutrients and oxygenation capacitywould be desirable.

SUMMARY OF THE INVENTION

The preceding problems are addressed by the generation and introductionof specific biology populations with modified characteristics in storedsubstances, such as macro nutrients and carbon-based compounds, andwhich are customized to optimize waste treatment process by performingspecific tasks during the main treatment processes while maintainingminimal solids growth. These bacteria may be grown from specializedmixes of activated sludge and waste influent by exposing these materialsto controlled growing environments, e.g., in an isolated off-linetreatment area. The off-line environment is also controlled toselectively stress the population developed in the on-line treatmentprocess that does not have the desired characteristics of low growth oryield. The resulting modified population may be added back to the mainprocess to optimize further treatment of the waste stream by performingsuch tasks as improving nitrification/denitrification efficiency, orachieving target levels of desirable biological make-up, such as, forexample, increasing the population of facultative anaerobic bacteriawhile minimizing sludge yield. To achieve its objectives, the inventionrelies upon on-line measurements of oxidation reduction potential(“ORP”) and pH while also monitoring and controlling release andgeneration of ammonia, nitrate, and phosphorus.

Generally, in one aspect, the invention provides for the treatment of awaste stream using a growth method that involves conducting a portion ofthe waste stream to a first treatment vessel and contacting it with afirst biological population having a first population profile. Themethod further involves drawing off a portion of thusly-treated wastestream to an off-line treatment vessel and isolating it. The drawn-offportion is controlled in the off-line treatment vessel to establish asecond biological population having a second population profile that isdifferent from the first population profile. The controlling stepincludes monitoring levels of at least one of ORP and pH, and monitoringcontent of at least one of ammonia, phosphorus, and nitrate to optimizefurther treatment of the waste stream while minimizing sludge yield,e.g. to achieve a target level of a desired biological make-up, such asfacultative anaerobic bacteria. The controlling step, responsive to themonitored content levels, may include allowing an ORP level to decrease,causing a content of at least one of ammonia and phosphorus in thedrawn-off portion to increase until a desired content value is achieved.For example, the controlling step may include allowing an ORP level todecrease, causing release of at least one of ammonia and phosphorus frombiological destruction and external biological substance solubilization.

Other embodiments of the invention include allowing the ORP level in thedrawn-off portion to decrease to a variable set point for a selectedperiod of time, causing release of ammonia and phosphorus, as well asmodifying and/or destroying a portion of the biological population. Thiscan be continued until desired ammonia and/or phosphorus content isdeveloped and/or a corresponding negative ORP level set point ismaintained for a certain period of time. The process step can becontrolled by acting on the drawn-off portion, by, for example, aerationand mixing, such that the ORP level is raised to a higher value, oruntil the pH is reduced to a lower set point value or a period of timefor aeration and mixing is exceeded. Nitrates will be developed duringthe aeration and mixing step. Terminating aeration and/or mixing willdecrease the ORP level and cause ammonia and phosphorus to release whilenitrates are consumed. While the ORP level decreases with no aerationand mixing, nitrates and subsequent aeration and mixing can control theORP level at sufficiently high levels to prevent significant sulfatereduction, while modifying and/or destroying biology and biologicalmaterial until a desired ammonia and phosphorus content is released.Embodiments also include using aeration to increase the ORP level andgenerate nitrates, a significant source of oxygen for facultativeoxidation. This can be continued until the pH level begins to decrease.The ORP rate of change can be altered by the addition of raw influentand the increasing duration of settled unmixed cycles.

Settling can be used during the controlling step to produce a decantablevolume of clarified liquid high in ammonia and/or phosphorus or nitratesdepending on the timing of the decant with mixing and aeration. Afraction of the drawn-off portion including a portion of the secondbiological population can be taken from the off-line treatment vesseland returned to the first treatment vessel if decanting while mixing ormixing is timed to occur during a portion of the decant cycle. Ammoniaand organic nitrogen from the decantable volume can be added to thefirst treatment vessel as an oxygen source. The nitrate oxygen sourcecan be used in the first treatment vessel as a mechanism to raise theORP of the first treatment vessel, provide a significant source ofoxygen, and limit the population of filamentous bacteria.

The ORP level of the off-line treatment vessel environment can becontinuously monitored during both mixing and settling. Operating rangesof ORP and pH can be adjusted to release ammonia and phosphorus from thedrawn-off portion. The ammonia and phosphorus release and subsequentoxidation and uptake can be adjusted to control the profile of thesecond population prior to return to the first population. For example,the controlling step may include maintaining the ORP level by adjustingfor changing temperature of the off-line treatment vessel within atargeted temperature range. The solubilization and destruction thatgenerates ammonia and phosphorus is accelerated by increasingtemperature. In various embodiments, during ammonia and phosphorusrelease, a biologically significant amount of carbon is available toallow for simultaneous nitrification and denitrification at the outsetof the aeration cycle, which further mediates the loss of alkalinity anddecrease in pH level typically found in aerobic digesters.

In some embodiments, the off-line treatment vessel can be operated in acollector mode. In various embodiments of the invention, there is noflow of population between the off-line treatment vessel and firsttreatment vessel during the controlling step. The second populationcharacteristics are further modified and controlled to include controlof solids concentration, concentration of inerts and non-biologicalmaterial, further reduction and control of the first population profileinherent in the second population profile.

Embodiments of the invention provide for the treatment of a waste streamusing growth methods that involve mixing a portion of the stream withactivated sludge and then using off-stream controls of mixing, airexposure, residence time and settling sequences with no mixing or airexposure to create specialized population profiles. These specializedpopulations have characteristics that are useful in achieving particulardesired results when treating the incoming waste, oftentimes incombination with, or as a pre-existing component of the main treatmentprocess.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing discussion will be understood more readily from thefollowing detailed description of the invention, when taken inconjunction with the accompanying drawings, in which:

FIG. 1 shows a waste treatment process, representing a basic flowsequence that is well-known in the art and to which the presentinvention may be applied;

FIG. 2 illustrates the ORP ranges in which different types of biologypopulations tend to predominate; and

FIG. 3 is a schematic depiction of an apparatus that may be used toimplement the present invention.

DETAILED DESCRIPTION

The bacteriological populations used to treat wastewater and itsresiduals may be adjusted and controlled by the off-line manipulation ofboth an aerobic stress/destruction and a growth environment. Such agrowth environment may be conveniently established in equipment that isnot regularly used within an existing waste treatment process. Forexample, an aerobic digester previously used as a terminal solidshandling device may be used as an extension of the wet stream treatmentprocess in one or more embodiments of the present invention.

By these means conditions may be generated that favor low solids-yieldmicroorganisms, high removal-efficiency microorganisms, provide high orlow load return material for the main treatment process, minimize theformation of filamentous biology, and/or provide for the consumption ofresidual sludge (to minimize its volume). These and other biologicalclasses may be formed by the methods and apparatus disclosed below.These may also be used to provide enhanced quantities of desirablenutrients, additional oxygenation capacity, increased conversion ofparticulate carbon to solubilized cBOD, and reductions in disposalvolume for certain nutrients.

One way to quantify the operating characteristics of a water orwastewater treatment facility is by ORP, the techniques of which arefamiliar to those skilled in the art. As seen in Table 1, growth offilamentous Norcardia sp. is especially favored in an ORP range of about−50 to +50 mV which range is also typified by low dissolved oxygencontent (microaerobic) concurrent with low amounts of soluble cBOD.These preferred conditions for growth and replication of Norcardia sp.result in their enhanced population which gives unfavorable settling andhigher yield characteristics to the overall biological population andsuspended solids of the main treatment process. Hence, waste treatmentplant operation is hindered by maintaining conditions in thismicroaerophilic range that may be necessitated by high plant throughputrates.

TABLE 1 ORP Range (mV) Example Biology Region Obligate anaerobic <−400Methanogens Facultative <−400 to <−200 Sulfate reducing bacteria,anaerobic Acidogens Facultative aerobic −200 to +150 Bacillus spp.,Pseudomonas spp, Microaerophilic −50 to +50 Norcardia sp., Type 1701,Sphaerotilus natans Obligate aerobic +50 to +200 Nitrosomonas andNitrobacter Condition Aerobic  >+50 Anoxic −150 to +50 Anaerobic <−150

These and other factors may be mitigated by the present invention. Forexample, a mixture containing certain amounts of waste influent andwaste activated sludge may be customized by controlling factors such assolids content, residence time, mixing with air, mixing without air,subsequent addition of influent or sludge, and/or the selective removalof certain fractions of the mixture to achieve certain biologicalresults including the demise of certain biological populations, theenhancement of other, preferred, populations and the modification of theprofile in surviving populations different than what is generated duringwith the on-line process.

The invention may be used in several modes. In the “selector” mode anoff-line mixture is customized to provide a particular biologicalprofile for return to the main treatment process that will favor thepresence of one or more classes of microorganisms, and disfavor thepresence of microorganisms that are adverse to the processingobjectives. The desired combination of favorable and unfavorableconditions for growth is obtained in the selector as described herein.When the desired biology is returned to the main treatment process,providing a desired biology population with even a slight populationadvantage may result in a significant operational enhancement over time,because the competitive balance between the populations will have beenshifted.

The invention may also be operated in the “collector” mode, whereby theoff-line process is operated as a digester, with the goal of minimizingthe yield of solids and collecting these for disposal. Thus, incollector mode, the off-line mixture is concentrated with or withoutadditional treatment. The combined effect of these two modes ofoperation is minimizing the quantity of residual solids for ultimatedisposal beyond what would normally be possible if a system wereoperated in a conventional fashion while enhancing the performance ofthe main process.

Elutriation with raw influent waste is one technique that may be usedfor the generation of specialized biology populations. Traditionally,elutriation as used in waste treatment processes would be for thepurpose of reducing the inorganic content of a specific volume of wastesolids by dilution with water of a lesser inorganic content (dissolvedor undissolved). In the present invention, elutriation involvesexchanging the free water of dilution during the selection process toachieve reduced inorganic content while concurrently increasing theorganic content of the volume by adsorption and absorption of cBOD fromthe raw influent waste. This exchange of reduced inorganic contentconcurrent with increased cBOD is used to strategically favor theformation of the class of biology desired as those classes capable ofcapture and retention of “food” will have a competitive advantage forgrowth and replication. Directly related is the technique of strategicintroduction of high strength influent flow in the absence of oxygen(air) supply to a given biological population. Introduction of thismaterial during the mixed/unaerated cycle results in a competitiveadvantage to those species capable of fixing and retaining cBOD and/orNBOD for subsequent growth and replication. The present invention usesthese techniques in off-line processes for the specific enhancement ofbiological populations and provides for their use in the mainstreamtreatment processes by production of such high strength (high cBOD)streams that may be delivered to the main treatment process underconditions of controlled time, amount, and “introduction environment” tothe on-line process. Since the selector process output is returned tothe main treatment process, there are no effluent discharge complianceissues that limit how far the process may be pushed, and so the processmay be operated to fully maximize the biological results achieved.

Another significant aspect of the invention is the release of carbon,ammonia, and phosphorus in the off-line treatment vessel. What had beenincorporated within the biology in the on-line treatment vessel isreleased during the extended off-cycle with low ORP. The extendedoff-cycle generates carbon and nutrient release under conditionsfavorable to a low-yield, proper settling population. The subsequentre-incorporation of the solubilized carbon, ammonia, and phosphorus untothe second population with improved settling characteristics for returnto the on-line treatment vessel.

Customized biological populations may be generated to achieve specificobjectives. Example 1 below teaches how to generate a biologicalpopulation that converts particulate cBOD into soluble cBOD forutilization. The population of organisms selectively enhanced allows forgeneration of a high cBOD stream to be returned under controlledconditions and for generation of a biological population that hasgreater capacity for reduction of particulate to soluble cBOD. This isuseful to reduce solids content, or to provide food during periods oflow influent BOD content to help sustain the existing population ofmicroorganisms. Example 2 below teaches how to generate low-yieldbacteria. Use of these microorganisms results in less residual solidsformation, such that disposal quantities and costs are reduced.Additionally, the lower solids content results in energy savings sincefewer solids need to be processed and transported through the mainstreamprocesses.

The embodiment of Example 3 teaches how to improve the yieldcharacteristics of the whole while concurrently improvingnitrification/denitrification capability and capacity. This invention isparticularly useful for facilities that have difficulty meeting theirenvironmental effluent discharge requirements for nitrogen content.Example 4 teaches a method for reducing the formation of filamentousbiology. These microorganisms are especially troublesome for plantoperation and efficiency in that they do not settle well, do not filterwell, and are largely gram positive (a general characteristic of highsolids yielding species).

Example 5 teaches a method for the off-line minimization of residualsolids content, prior to disposal. Operated as a collector subsequent tooperation in selector mode, the method of this example may be employedrepetitively until further consumption and denitrification is no longerachieved after the residual solids have been minimized by specificselection techniques embodied in the present invention. Example 6teaches a method for the reduction or optimization of facultativeanaerobes profile while monitoring ammonia, phosphorus, and nitratelevels. The method can be used to generate nitrates, which can be usedas an oxygenation source in a treatment process.

The embodiment of Example 7 teaches a method to create phosphateparticles of increasing size. Use of this technique in a treatmentprocess allows environmental discharge standards to be met using reducedamounts of flocculent/coagulant. Example 8 teaches a method that usesaccelerated cycles of high aeration intensity to degrade biologicalmaterial external to the microbial population. This technique can beused to enhance the results of Example 2.

Lastly, Example 9 teaches a method to generate a process seed having anincreased carbon uptake capacity. The resulting seed mixture can beadded to a treatment process to facilitate the treatment of a wastestream.

As illustrated in FIG. 2 and in Table 1, various types of microorganismsthrive in environments of different ORP ranges. Dissolved oxygen contentis not always indicative of ORP. Other methods may be employed tomeasure which microorganisms are favored, such as Specific Oxygen UptakeRate (SOUR), Specific Nitrogen Uptake Rate (SNUR), pH, phosphorus,ammonia or nitrate content. The operational control of the sequence ofconditions by ORP, SOUR, SNUR, pH, phosphorus, ammonia, or nitratecontent, or other description of biological conditions is not intendedto be all inclusive, limiting, or otherwise required for theimplementation of various embodiments.

Also affecting the biological selectivity is the quantity of biologicalsolids present. As waste treatment plant throughput rates increasegenerally so also do the volumes of residual sludge produced, requiringincreased amounts of solids to be sent out for disposal. Increased plantthroughput normally is thereby linked to increased disposalrequirements. The fixed volume available for processing the influentmandates that the treated materials spend less time within the confinesof the treatment process, including the generated solids. However, someplants have additional solids retention capability, thereby altering theratio of solids to influent and impacting the inherent biologicalselectivity. This variation in solids content is not known to be ofpractical usefulness to those who operate waste treatment plants.Control of the fraction of biological solids, and in particular theoverall reduction of its amount as a whole is used to advantage by thebiological selection process of the invention.

As mentioned earlier, some waste treatment plants supplement theincoming waste flow with nutrients to support the biological treatmentprocesses. For example, as detailed below, the invention may be used togenerate high- or low-load return to the treatment plant. Low-loadmaterial is typically high in ORP and may be also high in nitratecontent, while high-load material is generally low in ORP and may behigh in one or more of soluble cBOD, phosphorus, ammonia, and/or organicnitrogen. This choice may be made during selector operation virtuallyindependent of the selection process, allowing these return materials tobe strategically chosen and provided to the main treatment processduring the appropriate portion of the diurnal cycle.

Nitrogen, commonly present in the form of ammonia or nitrate, can beconsidered to be another biological nutrient in treatment processes, andsometimes needs to be added to the incoming waste flow. However, usingammonia and nitrate monitoring in addition to pH and ORP analyses allowsthe control of the nitrogen reactions to be improved. A drop in the ORPlevel can be used to detect ammonia release from the biomass, andconversely, excessive ammonia release corresponds to an ORP drop thatwill generate significant sulfate reduction. Ammonia release is alsoaffected by time and increased temperature, in the absence of air andmixing. However, monitoring and control of ammonia and nitrate levelscan be used to maximize the ammonia release while preventing excessivesulfate reduction and odor generation, such that the biologicalselection of facultative anaerobic bacteria profile is optimized whilethe destruction of an aerobic bacteria profile is optimized forsubsequent return to the online waste treatment process.

Notably, the on-line treatment process preferably needs to staysufficiently aerobic to maintain efficient water quality standards thatare low in ammonia, phosphorus, and carbon (CBODs) content. Thesematerials are released when the first population profile is stressedwith low ORP environment, as found in the off-line reactor disclosedherein. The materials are released to the surrounding water as afunction of the initial population profile stress, destruction, andsolubilization of external biological substances. The anoxic andanaerobic environment release of this material for re-growth under lowORP/low yield conditions is generally contrary to aerobic treatmentrelease of these materials under high energy and high yield conditionsin the on-line process or the terminal process for solids in aerobicdigesters. Thus, the selective destruction referenced above occursbecause the biomass profile was formerly unavailable for ammoniaformation during aerobic processes. After sufficient ammonia generationhas occurred, air is added to raise the ORP and to oxidize the generatedammonia, resulting in nitrate formation. Aeration is generally stoppedafter a selected period of time, once an increased ORP set point isreached or the pH level begins to decrease. The drop in pH levelindicates a loss of alkalinity from ammonia oxidation. It is also causedby the aeration and treatment of organics that were formed while theammonia was being released. Techniques such as these can be of benefit,for example, in the following situation.

If the treatment plant is underloaded, a low-ORP, high-load returncontaining organic and nitrogen oxygen demand may be provided to helpfeed the microorganisms in the aeration process. Conversely, a high-ORP,low-load return might be preferred for times when the plant requiresoxygenation assistance, in which case the high nitrate content also maybe used to help sustain the facultative biology with combined oxygen(see, e.g., Example 6). In this manner the filamentous microaerophilesare stressed by a reduction in available food and improved free oxygenlevels, helping to reduce the organic demand and allowing the aerationprocess to have sufficient aeration capacity during otherwise highloading periods to attain high ORP conditions in the mainstream process,further discouraging filamentous organisms.

The technique is especially useful for plants that have excessiveorganic loading and cannot aerate their way beyond or above thepreferred filamentous formation range. The combined oxygen contained inthe nitrates allows BODs uptake by the facultative anaerobes and reducesthe BODs oxidation that must occur with limited free oxygen. The highORP nitrate return can be used to provide for combined oxygenintroduction to immediately start removing BOD/cBOD. (To preventfilament formation, it would be necessary to operate without marginalresidual oxygen until the BOD is removed by adsorption, absorption, orconversion to gases, then aerate to ORP levels above the preferredfilament formation range.) Without use of the present invention, thesteps required to avoid preferential conditions for filamentousorganisms would limit the throughput capacity of the treatment plant.The situation is exacerbated at high food-to-microorganism (F/M) ratios,where an ever-increasing amount of dissolved oxygen is required toprevent the formation of filamentous biology.

However, for situations such as these where the aeration system of themain process flow is unable to provide adequate oxygenation to avoidexcessive filamentous growth, then the high-nitrate source generated bythe invention may be used to supplement the oxygen supply. In thismanner the nitrate source may be used during times of peak influentflows to supplement the aeration process, thereby preventing themicroaerophiles (filamentous biology) from taking advantage of the lowdissolved oxygen conditions. Proper sequencing of the selector operationmay thereby be provided to match selector return with the peak demandrequirements of the main treatment process. Further benefits may beobtained concurrently by off-line selection against filamentousorganisms and/or by selection of biological populations that are bothmore efficient in their use of oxygen (facultative aerobes) and/or byselection and preferential cultivation of populations that do notrequire oxygen sources for conversion of cBOD to gases.

Another embodiment of the invention, still operating in selector mode,facilitates minimizing the solids volume a waste treatment plant mustsend out for disposal. Off-line operating conditions are selected whichenhance the population of low-yield organism profile to the equilibriumpoint where the death and decay of the organisms is offset by the loweryield generation (i.e., the increase in biological solids is balanced bythe reduction in overall solids yield), or by operation of the processto accelerate the decay sufficiently to achieve that same equilibrium.This may be achieved by decreasing the ORP to <−150 mV, or preferably to<−200 mV and lower then increasing the ORP to >50 mV, or preferablyto >100 mV and higher. The ORP level ranges are dependent on siteconditions and may vary from plant to plant. The resulting biologicalpopulation may then be used to augment the solids of the main processflow resulting in minimization of the solids generated initially andconcurrently helping the effluent to comply with discharge water qualityrequirements.

Elements of the same method may be used to advantage in the collectormode of operation, when a limited amount of non-degradable content ispresent. This method is detailed in Example 5 below. Operation of theterminal treatment/stabilization process serves to minimize the overallamount of material that must be disposed of by a waste treatment plant.By this method residual solids are converted to solubilized biomass andreturned to the main treatment process for consumption. In collectormode, the residual non-solubilized materials are disposed of aftermaximizing the solids content to achieve minimum solids volume forsubsequent processing. The proportional frequency of operating in“selector” mode versus the terminal “collector” mode is determined bythe amount of non-degradable content of the influent material to betreated. The number of cycles performed by the collector to concentrateand maximize a given mass of material is limited primarily by the ratioof biological solids to non-degradable materials and by the relativeamount of non-degradable content originally present.

Another, albeit indirect, method to reduce solids disposal volumesrelates to phosphorus control. Phosphorus is a biological nutrient thatcan be present in waste treatment streams in amounts greater thanallowed by environmental discharge regulations. Chemical additives suchas flocculating and coagulating agents are commonly added to solutionscontaining soluble phosphorus (sometimes in the form ofortho-phosphate), causing the phosphorous particles to precipitate andthose particles to floc together out of solution. The addition of thesechemical agents for this purpose results in increased sludge disposalvolumes, not only because of the resulting phosphate precipitant, butalso because it is necessary to dispose of these additives. Theinvention includes methods to precipitate phosphorus without requiringthe use of such additives, if the native water chemistry has othernaturally occurring compounds available to generate a precipitate underthe cycling conditions between low ORP and high ORP disclosed herein.

Phosphorus precipitation can be accomplished as described below, withoutrequiring the use of flocculating or coagulating agents (see, e.g.,Example 7). Re-aeration of a previously un-aerated biological mixturecan cause incremental precipitation of previously solubilized phosphate,due to a pH increase caused by carbon dioxide stripping during theaeration cycle. Under the low ORP, non-mixed condition, bacterialrespiration continues in a micro-environment of low pH due to theexcessive carbon dioxide that is not stripped by mixing and aeration.The phosphorus content in the liquid is increased as phosphorusaccumulating organisms (“PAOs”) incorporate the carbon that has beensolubilized with low ORP. The PAOs continue to respire, releasingphosphorus. Also, very small phosphorus compounds that exist asacid-soluble alkalinity are dissolved and continue raising thephosphorus content in the liquid and lowering the phosphorus content inthe solids. When mixed and aerated, there is a rapid increase in pH. Thecommon ion effect of high phosphorus reduces compound solubility andthere is a precipitation of phosphorus as a chemical precipitate.Smaller seed particles grow into larger particles with less surface areafor a given mass. The reduced surface by mass continues with eachsuccessive cycle of solubilization and precipitation caused by thecycling according to various embodiments of the invention.Phosphorus-based alkalinity is less available for release while PAOshave less phosphorus available for biological uptake. Overall, thebiological and chemical profiles improve the on-line treatment as thesecond population of solids is returned to the on-line system. Repeatedaeration/non-aeration cycles result in the formation of increasinglylarger particles of phosphate-based compounds, beyond the amount thatwould ordinarily be achieved by just a population of PAOs. Once ofsufficient size, these particles can be discarded with the sludgecustomarily generated by waste treatment processes. However, the sludgevolume to be discarded is reduced since this phosphate-based precipitantdoes not contain the chemical additives used with previous technologies.

Moreover, it is believed that the amount of phosphorus precipitation canbe increased by the artificial introduction of carbon dioxide beyondwhat is achieved through biological respiration. Respiration of thebiomass in high-load mixtures produces carbon dioxide that facilitatesphosphorus release, and biomass (such as influent or return activatedsludge (“RAS”) can be added for this purpose. Since such carbon dioxiderelease is reduced in low-load mixtures, careful controlled exposure ofthe phosphorus precipitation reaction to an external source of carbondioxide can allow the phosphorus release rates of low-load mixtures toapproach those of high-load mixtures (see Example 7). Furthermore, eventhe phosphorus release rates of high-load mixtures can be enhanced bythe addition of carbon dioxide. Therefore, for both high- and low-loadmixtures, better removal of phosphorus can be achieved with loweroverall sludge yield since the process is not limited by a carbon sourceand natural release of carbon dioxide. Of course, chemical additives canbe used in combination with these techniques to further removesolubilized phosphate from treated waste streams.

Principles of the invention can be combined with proprietary (e.g.,Example 8) and/or conventional (e.g., Example 9) treatment technologiesto achieve synergistic effects. For example, an aeration step isemployed in many of the examples provided. Commercially-available onlineaeration processes such as the ORBAL (trademark of U.S. FilterCorporation, Palm Dessert, Calif.) and Vertical Loop Reactor (“VLR”)(trademark of Envirex Inc., Waukesha, Wis.) technologies exposebiological processes to an accelerated cycle of high aeration intensity,followed by anoxic conditions. However, in these processes it isacceptable to introduce an external carbon source such as influent, seedpopulation, or RAS due to the high oxidation demand environment. Sinceembodiments of the present invention limit carbon source materials todrive the loss of oxidation pressure, the resulting reaction rates ofthe invention are much slower due to a reduction in the metabolic rate.Therefore, use of the invention in combination with online, pulsedaeration technology such as the ORBAL or VLR processes allows theinvention to be practiced at a much higher throughput rate. Theselection of facultative anaerobes and degrading of the materialexternal to the microbial population is thereby accelerated.

The principles of the invention can also be combined with conventionalprocesses and techniques commonly used in waste treatment plants toachieve synergistic results. For example, seed materials such as thoseproduced in the Examples below can be combined with an external carbonsource (such as influent) and held in an anoxic and/or aerated anoxiccondition for an extended period of time. This imparts further stress onthe biological mixture and can further improve the biological selectionand metabolic uptake of carbon. Addition of this material to an upstreamportion of the plant (prior to the biological treatment portion of theplant), such as a flow equalization vessel or a wet well that feeds thecoarse removal equipment 110, results in subsequent exposure of themixture to pumping, screening and degritting operations. Exposure ofthis mixture to these physical and mechanical stresses, and tosubsequent cycling of aerobic and anoxic conditions, enhances thetreatment while maintaining the low yield characteristics of the secondpopulation.

Many of the methods summarized above may be conveniently implemented bythe apparatus illustrated in FIG. 3. Such an apparatus may beconveniently and inexpensively obtained by making slight modificationsto old, perhaps unused waste treatment plant equipment, such as an olddigester. The apparatus comprises a vessel, such as a tank 130, a supplyof waste solids 132, a supply of raw influent 134, a supply of effluent135, a mixer 136, a supply of air or oxygen 138 (either or both of thesemay be used effectively), an upper removal device 140 to remove, atvarying elevations, volume such as decant from near the surface 142 ofthe liquid under treatment, and a lower removal device 144 to removevolume from near the bottom of the tank 130. Upper removal device 140may consist of, for example, a variable-height overflow weir located atthe perimeter of the tank 130, or it could be an internal overflow weirwith a variable height adjustment. The height adjustment could beachieved by elevating or lowering the inlet end of the weir, or byhaving multiple input points at varying elevations and blocking off theinput points from which the decant flow is not desired, therebyproviding for a controllable decant amount. This blocking can be done byvarious means, automated or not.

The apparatus of the invention, or other equipment suitable forperforming the methods of the invention, can generally be used in eitherthe selector mode or the collector mode of the invention. Such equipmentcan be used to provide an offline, controlled growing environment inwhich selected biological materials are isolated, sequentially exposedto or isolated from various environmental factors and stimuli, andcontrolled to promote desired chemical and biochemical results. In manyinstances these reactions are forced to equilibria not previouslyachievable in commercial or municipal online processes, by usingbatch-mode, offline sequential control processes. Use of such techniquesin batch processes isolated from the constraints of the continuous flowprocesses of a conventional waste treatment plant allows such extremeresults to be achieved. Batch operations are distinguishable fromcontinuous flow processes in that during processing there are steps ortimes during which there is no flow of water or biological materials toor from other processes. Of course, treatment using continuous flowprocesses can also be performed in the equipment of the invention, butthe most favorable results are generally achieved when the timeconstraints of continuous flow processes are avoided by utilizing batchoperations. Isolation from the real time constraints of known treatmentprocesses allows extended residence time to be utilized for certainprocessing steps as required, and as discussed below.

Specific embodiments of the invention may negate the need for one ormore of the above-listed requirements, and they may be implemented indifferent ways. For example, the mixer may be oriented vertically orhorizontally, and supported and/or driven from the top, bottom or theside of the vessel or a pump may be used for mixing internallytransferring bulk liquid flows from one location to another within thetank. The supply of air or oxygen 138 may be introduced by differentmeans, from above or below the liquid surface, and different input ratescan be used. The apparatus described is effective for performing thesteps of the methods detailed below.

In operation, the illustrated apparatus serves as an off-line processingenvironment facilitating growth of customized biological populations.New influent received from the main treatment process via line 134 isjudiciously combined with appropriate excess or waste solids to achievethe necessary growth conditions. Decanted liquid obtained from upperremoval device 140 is returned as appropriate to the main treatmentprocess. Material including beneficially derived biological populationsare removed via lower removal device 144 and returned to the maintreatment process when operating in selector mode, or disposed of whenoperating in collector mode. The following examples may be practicedusing a device as discussed above, and are presented for purposes ofillustration and are not intended to limit the application of theinvention.

EXAMPLES Example 1

The following procedure selects for facultative anaerobes, independentof nitrifiers, at the expense of obligate aerobes, to specificallyaugment biology that rapidly breaks down particulate cBOD into solublecBOD for utilization.

-   -   1. Fill tank 130 with a combination of excess activated sludge        and raw influent, providing a nominal suspended solids        concentration of between 3,000 and 5,000 mg/liter.    -   2. Mix contents of tank 130 using mixer 136 without aeration        until the ORP is anaerobic, but not so low as to evoke sulfide        generation by sulfate reducing bacteria, should there be sulfate        present in the raw influent or waste sludge. The mixture can        also settle (without mixing) to accelerate the drop in ORP. This        mixing and settling should last for about 4 to 8 hours.    -   3. Stop the mixing and allow the mixture to settle, providing a        decantable volume of at least 25% of the volume of tank 130.        This will require about 2 to 4 hours.    -   4. Remove the high cBOD, high ammonia, low ORP (“high load”)        decant material via the upper removal device 140 to the plant        treatment process when desired.    -   5. Replace the removed volume with raw influent and repeat steps        2 through 4 until the remaining suspended solids content reaches        7,500 to 10,000 mg/liter. This will generally require between 4        and 10 repetitions of these steps.    -   6. While mixing with mixer 136, return about half of the volume        of tank 130 to the plant treatment process.    -   7. Repeat steps 1 through 6 as necessary.

Example 2

The following procedure selects for facultative anaerobes and aerobes,preserving nitrifiers, at the expense of obligate aerobes, tospecifically augment biology low in yield. This is particularly usefulfor the minimization of residual solids.

-   -   1. Fill tank 130 with a combination of excess activated sludge        and raw influent, providing a nominal suspended solids        concentration of between 5,000 and 7,500 mg/liter.    -   2. Mix contents of tank 130 using mixer 136 without aeration        and/or settle until the ORP is anaerobic, but not so low as to        evoke sulfide generation by sulfate reducing bacteria, should        there be sulfate in the raw influent or waste sludge. This        mixing should last for between 8 hours and 3 days.    -   3. Continue mixing with mixer 136, and aerate tank 130        “aggressively” until the ORP is >100 mV for 24 hours, >150 mV        for 12 hours, or >200 mV for 4 hours.    -   4. Stop the aeration but continue mixing until the ORP is        anaerobic for at least 48 hours. If the ORP does not continue to        decrease by at least 10 mV per hour, add 3-10% by volume of raw        influent.    -   5. Stop the mixer 136 and allow the contents of tank 130 to        settle, to provide a decantable volume of at least 25% of the        volume of tank 130. This will take approximately 2 to 4 hours.    -   6. If a high load return is desired, decant to the treatment        process.    -   7. If a low load return is desired, aerate the mixture and mix        using mixer 136 until the ORP is >100 mV for 1 hour. Then stop        the mixing and aeration, allow settling and then decant to the        treatment process.    -   8. Replace the decanted volume with excess activated sludge from        the supply of waste solids 132, only as along as the solids        content remains <7,500 mg/liter. If they are higher then dilute        by addition of raw influent.    -   9. Repeat steps 2 through 6 twice.    -   10. While mixing with mixer 136, remove ⅓ of the volume of tank        130 to the treatment plant process.    -   11. Repeat steps 1 through 8 as necessary, taking care to        maintain the suspended solids concentration below 10,000        mg/liter, and preferably at less than 8,000 mg/liter.

Example 3

The following procedure selects for facultative aerobes and nitrifiersto reduce high yield organisms, and improves thenitrification/denitrification capacity. If available, a recycle streamhigh in ammonia and cBOD content can be used in place of, or incombination with the raw influent, as long as the cBOD (mg/liter) toNH₃—N (mg/liter) ratio is greater than 3. Note that this ratio isreferenced to ammonia nitrogen, not Total Kjeldahl Nitrogen (TKN).

-   -   1. Fill tank 130 to approximately 75% full with activated sludge        at a suspended solids concentration of between 2,500 and 7,500        mg/liter.    -   2. Mix contents of tank 130 using mixer 136 and with aeration        and/or settle until the ORP is aerobic and the ammonia content        is <0.1 mg/liter.    -   3. Stop the aeration.    -   4. With continued mixing, fill about another 5 to 10% of the        volume of tank 130 with additional raw influent. Monitor the ORP        and nitrate concentrations until the nitrate concentrations are        <0.1 mg/liter. This will take approximately 2 to 4 hours.    -   5. Continue to mix the tank contents, and begin to aerate tank        130 until the ORP is >100 mV for 4 hours, >150 mV for 2 hours,        or >200 mV for 1 hour, and the dissolved oxygen concentration        is >3.0 mg/liter for about 1 hour.    -   6. Stop the mixing and aeration for at least 4 hours, or until        the observed dissolved oxygen concentration is <0.2 mg/liter,        whichever is longer.    -   7. Repeat steps 4 through 6 two more times.    -   8. Remove the top 25% of the volume of tank 130, as decant. If        there are suspended solids within this 25%, remove them also.    -   9. Repeat steps 4 through 8.    -   10. Restart the mixing, and remove another 25% of the tank        volume to the plant treatment process.    -   11. Replace the volume removed in step 10 with excess activated        sludge, maintaining the solids concentration at <7,500 mg/liter.        If necessary, add additional raw influent to keep the solids        concentration below this level.    -   12. Repeat steps 2 through 11 as necessary.

Example 4

The following procedure selects for facultative anaerobes andfacultative aerobes, to generate a low yield biology population. Itdisfavors the formation of filamentous biology, such as Norcardia sp.

-   -   1. Fill tank 130 to at least 90% full with excess activated        sludge, providing a nominal suspended solids concentration of        between 3,000 and 10,000 mg/liter. Dilute the mixture with raw        influent as required to keep the solids content below 10,000        mg/liter. Any dilution required may be done with plant effluent        or mixed liquor from the main process flow, but the use of raw        influent is preferred.    -   2. Mix contents of tank 130 using mixer 136 without aeration        and/or settle until the ORP is anaerobic, but not so low as to        evoke sulfide generation by sulfate reducing bacteria, should        there be sulfate present in the raw influent or waste sludge.        This mixing could last for between 8 hours and 3 days, depending        upon the ambient temperature and the temperature of the mixture.        If the ORP stabilizes at over −200 mV, then add 5% by volume of        raw influent to the mixture, while mixing with mixer 136.    -   3. Turn off the mixing and wait for 48 hours, but mix the        contents for a one hour period after 24 hours have passed. This        needs to be done without aeration.    -   4. After the 48 hour period, resume mixing with mixer 136 and        aerate the contents of tank 130 “aggressively” until the ORP        is >100 mV for 16 hours, >150 mV for 8 hours, or >200 mV for 4        hours.    -   5. Repeat steps 2 through 4.    -   6. Stop the mixing and aeration and allow the contents to settle        for not more than 2 hours.    -   7. Remove to the treatment process all of the decantable volume,        or 20% of the volume of tank 130, whichever is less.    -   8. Add raw influent to tank 130 until it is 90% full. If        necessary, add excess activated sludge to maintain solids        concentration above 5,000 mg/liter.    -   9. Repeat steps 2 through 7.    -   10. While mixing with mixer 136, remove ⅓ of the volume of tank        130 to the plant treatment process.    -   11. Repeat steps 1 through 10 as necessary, taking care to        maintain the suspended solids concentration below 10,000        mg/liter, and preferably at less than 8,000 mg/liter.

Example 5

The following procedure explains how to operate the invention as acollector. Contrasted with the method of Example 2 above, the primaryobjective of this method is to minimize the disposal volume of anyresidual solids, rather than to provide a low-yield biology populationfor return to the waste treatment process.

-   -   1. Fill tank 130 with a combination of activated sludge and raw        influent, to provide a suspended solids concentration of between        5,000 and 7,500 mg/liter.    -   2. Mix contents of tank 130 using mixer 136 without aeration        and/or settle until the ORP is anaerobic, but not so low as to        evoke sulfide generation by sulfate reducing bacteria, should        there be sulfate in the raw influent or waste sludge. This        mixing could last between 8 hours and 3 days.    -   3. Start or continue mixing with mixer 136, and aerate tank 130        “aggressively” until the ORP is >100 mV for 24 hours, >150 mV        for 12 hours, or >200 mV for 4 hours.    -   4. Stop the aeration but continue mixing and/or settling until        the ORP is anaerobic for at least 24 hours. When the ORP is no        longer decreasing by at least 10 mV per hour, proceed to the        next step.    -   5. Stop the mixing and allow the tank contents to settle,        providing the maximum decantable volume achievable within 24        hours.    -   6. If a high load return is desired, then remove the decant to        the treatment process.    -   7. If low load return is desired, then aerate the mixture and        mix with mixer 136, and maintain this until the ORP is >100 mV        for a period of 1 hour. Then stop the mixing and aeration, allow        the mixture to settle to obtain the maximum decant amount        available as may be indicated by laboratory settleometer, and        then decant the low load material to the treatment process.    -   8. Replace the decanted volume with activated sludge of the        highest available solids content.    -   9. Repeat steps 2 through 6 until no further decant material is        generated upon settling, taking care to not fill the top 5-10%        of the volume in tank 130 with solids.    -   10. In a laboratory settleometer, without substantial aeration,        mix for 1 hour a sample consisting 90% of a representative        sample of the material contained in tank 130, plus 10% effluent.        Allow the mixture to settle for 24 hours. If the volume of        settled solids is less than 90% proceed to step 9 for further        treatment. Otherwise, remove the contents of tank 130 to the        solids disposal process as appropriate.    -   11. Add effluent to fill tank 130. Mix the contents with mixer        136 for between 1 and 4 hours, taking care to not aerate the        mixture.    -   12. Stop the mixing and allow the tank contents to settle.        Decant all available liquid.    -   13. Repeat steps 8 through 10 until there is no further increase        in solids concentration, whereupon the solids mixture is ready        for disposal.

Example 6

The following procedure optimizes the facultative anaerobe profile andincludes monitoring levels of ORP and pH with ammonia, phosphorus, andnitrate. Nitrate for use in a treatment process can be generated usingthis method.

-   -   1. Proceed through the steps 1-10 of Example 4 such that, using        procedures set forth therein, develop an acclimated biomass with        a low yield facultative anaerobe population profile in the        off-line reactor.    -   2. Following step 10, add a raw influent to tank 130 until it is        about 90% full.    -   3. Mix contents using mixer 136 without aeration. Mix for 15        minutes after the raw influent is finished being added.    -   4. Mix daily for no greater than 15 minutes as ORP decreases        below −100 mV.    -   5. Check ammonia and phosphorus release at each daily mixing.    -   6. As ORP drops below the negative set point less than −200 mV,        while tank 130 is mixed, check ammonia and phosphorus        concentration.    -   7. Once ammonia and phosphorus has stabilized between samples        with less than about 5 mg/L change, start mixer 136.    -   8. Once mixer 136 has operated for 30 minutes or longer, start        aeration.    -   9. Continue aeration and mixing until ORP is greater than +50 mV        or timed duration for the nitrification cycle reaches a set        point. Check ammonia, phosphorus, and nitrate levels. If ammonia        is greater than 10 mg/L, continue aeration. If ammonia is less        than about 10 mg/L, aeration is optional. Adjust an ORP set        point for nitrification cycle. If the ammonia concentration is        below 5 mg/L, confine set points, and continue with off cycle.        Check nitrate level.    -   10. If aeration continues past step 9 and if pH decreases more        than 0.2 s.u., stop aeration. Check ammonia, phosphorus, and        nitrate levels with operating set points of pH, ORP, and time        duration.    -   11. While mixer 136 is still operating, return no more than a        third of the tank volume to the on-line process.    -   12. Add excess activated sludge to tank 130 until it is 90%        full, and repeat steps 3 through 11. When necessary, add new        influent to maintain solids concentration below 10,000 mg/L or        to accelerate the decrease in ORP.

Example 7

The following procedure can be utilized to create phosphate particles ofincreasing size. Use of this technique in a treatment process allowsenvironmental discharge standards for effluent phosphorus control to bemet while maintaining a low sludge yield profile and reducing the amountof chemical addition for phosphorus precipitation.

-   -   1. Proceed through the steps of Example 6.    -   2. Continue to extend off-cycle times if phosphorus release        continues between sampling (greater than 5 mg/L per sample        time).    -   3. Check ORP negative step point with phosphorus release. Once        phosphorus release is stable or sulfate reduction is excessive,        based on odor generation at mixing and aeration, move to step 4.    -   4. Turn on mixer 136 for no greater than about 15 minutes, turn        on aeration cycle until pH level indicates a 0.2 S.U. decrease.    -   5. While mixer 136 is still operating, return no more than ¼ of        the tank volume to the on-line treatment process.    -   6. Add excess activated sludge to tank 130 until it is 90% full,        and repeat steps 2 through 5. When necessary, add new influent        to maintain solids concentration below 10,000 mg/L or to        accelerate the decrease in ORP.

Example 8

The following procedure uses accelerated cycles of high aerationintensity to degrade biological material external to the microbialpopulation. This technique can be used to enhance the results of Example2

-   -   1. Proceed through the steps of Example 2 with modified control        procedure as set forth in Example 6.    -   2. Couple off-stream reactor with the on-line pulsed aeration        process found in oxidation ditches and vertical loop reactors.    -   3. Ensure the off-line tank contents are returned to the on-line        process by mixing directly with the raw influent prior to the        on-line treatment process.

Example 9

The following procedure generates a process seed having an increasedcarbon uptake capacity. The resulting seed mixture can be added to atreatment process to facilitate the treatment of a waste stream.

-   -   1. Proceed through the steps of Example 6 to maximize the        facultative anaerobic profile with high nitrate discharge.    -   2. Return seed to the Biological Phosphorus Removal zone of the        on-line process.

The on-line process of anaerobic and anoxic zones provides for highcarbon uptake with a seed population that has been optimized for highcarbon uptake.

By the above it can be seen that a highly useful apparatus and methodshave been developed for improving the efficiency and effectiveness ofwaste treatment plant operations, both in terms of improving theirexisting treatment processes, and for minimizing the amount of wastedisposal volumes to be managed. The terms and expressions employedherein are used as terms of description and not of limitation, and thereis no intention, in the use of such terms and expressions, of excludingany equivalents of the features shown and described or portions thereof,but it is recognized that various modifications are possible within thescope of the invention claimed.

1-18. (canceled)
 19. A method of treating wastewater, the methodcomprising the steps of: conducting wastewater to a treatment vessel fortreatment comprising contact with a first biological population having afirst-biological population profile to produce a mixed liquor includingactivated sludge; separating the activated sludge from the mixed liquor;drawing off a first portion of the separated activated sludge andreturning said first portion to the treatment vessel; drawing off asecond portion of the separated activated sludge and adding that secondportion to at least one off-line treatment tank; controlling theoff-line treatment tank so as to produce, in the off-line treatmenttank, a second biological population having a second-biologicalpopulation profile different from the first-biological populationprofile, wherein the controlling step comprises subjecting the contentsof the off-line treatment tank to a selected sequence of at least twoconditions selected from the group consisting of an aerobic condition,an anoxic condition and an anaerobic condition, wherein the contents ofthe off-line treatment tank are maintained at each condition in thesequence for a corresponding determined length of time; and returning atleast a fraction of the produced second biological population to thetreatment vessel, wherein the second biological population achieveslower solids levels.
 20. The method of claim 19, wherein the step ofreturning at least a fraction of the produced second biologicalpopulation includes decanting a percentage of the produced secondbiological population from the off-line treatment tank.
 21. The methodof claim 19, wherein the step of returning at least a fraction of theproduced second biological population includes removing a percentage ofthe produced second biological population from the off-line treatmenttank.
 22. The method of claim 19, wherein wastewater is combined withthe second portion of activated sludge in the off-line treatment tank.23. The method of claim 19, wherein controlling the off-line treatmenttank comprises: i. mixing the second drawn-off portion without aerationto achieve anaerobic conditions without substantial sulfide generation;ii. mixing with aeration to achieve biological growth conditions withoutsubstantial production of obligate aerobes; and iv. mixing withoutaeration to achieve anaerobic conditions.
 24. The method of claim 19,wherein controlling the off-line treatment tank comprises: i. mixing thesecond drawn-off portion without aeration to achieve anaerobicconditions without substantial sulfide generation; ii. mixing withaeration to achieve biological growth conditions without substantialproduction of obligate aerobes; iii. mixing without aeration to achieveanaerobic conditions; iv. allowing settling to produce a decantablevolume; and v. mixing with aeration to achieve biological growthconditions without substantial production of obligate aerobes.
 25. Themethod of claim 19, wherein controlling the off-line treatment tankcomprises: i. mixing the second drawn-off portion without aeration toachieve anaerobic conditions without substantial sulfide generation; ii.stopping the mixing for a period of time; iii. mixing; and iv. mixingwith aeration to achieve biological growth conditions withoutsubstantial production of obligate aerobes.
 26. The method of claim 19,wherein controlling the off-line treatment tank comprises: i. mixing thesecond drawn-off portion of wastewater without aeration to achieveanaerobic conditions without substantial sulfide generation; ii. mixingwith aeration to achieve biological growth conditions withoutsubstantial production of obligate aerobes; and iii. stopping theaeration but continuing the mixing.
 27. The method of claim 19, whereincontrolling the off-line treatment tank comprises: i. mixing the seconddrawn-off portion of wastewater without aeration to achieve anaerobicconditions without substantial sulfide generation; ii. mixing withaeration to achieve biological growth conditions without substantialproduction of obligate aerobes; iii. stopping the aeration butcontinuing the mixing; iv. allowing settling; and v. mixing withaeration to achieve biological growth conditions without substantialproduction of obligate aerobes.
 28. A method for treating wastewater ina wastewater treatment system including a first treatment vessel forreceiving wastewater and for treatment including contact with a firstbiological population having a first-biological population profile, themethod comprising the steps of: drawing off a portion of the firstbiological population and adding said drawn-off portion to an off-linetreatment tank; controlling the off-line treatment tank to produce asecond biological population having a second-biological populationprofile different from the first-biological population profile, suchcontrolling including sequentially subjecting the contents of theoff-line treatment tank to a condition selected from an aerobiccondition, an anoxic condition and an anaerobic condition followed bysubjecting the contents of the off-line treatment tank to a differentcondition selected from the aerobic condition, the anoxic condition andthe anaerobic condition; and returning at least a portion of the secondbiological population to the treatment vessel.
 29. The method of claim28, wherein the step of returning at least a fraction of the producedsecond biological population includes decanting a percentage of theproduced second biological population from the off-line treatment tank.30. The method of claim 28, wherein the step of returning at least afraction of the produced second biological population includes removinga percentage of the produced second biological population from theoff-line treatment tank.
 31. The method of claim 28, wherein wastewateris combined with the drawn-off portion of the first biologicalpopulation in the off-line treatment tank.
 32. The method of claim 28,wherein controlling the off-line treatment tank comprises: i. mixing thedrawn-off portion without aeration to achieve anaerobic conditionswithout substantial sulfide generation; ii. mixing with aeration toachieve biological growth conditions without substantial production ofobligate aerobes; and iv. mixing without aeration to achieve anaerobicconditions.
 33. The method of claim 28, wherein controlling the off-linetreatment tank comprises: i. mixing the drawn-off portion withoutaeration to achieve anaerobic conditions without substantial sulfidegeneration; ii. mixing with aeration to achieve biological growthconditions without substantial production of obligate aerobes; iii.mixing without aeration to achieve anaerobic conditions; iv. allowingsettling to produce a decantable volume; and v. mixing with aeration toachieve biological growth conditions without substantial production ofobligate aerobes.
 34. The method of claim 28, wherein controlling theoff-line treatment tank comprises: i. mixing the drawn-off portionwithout aeration to achieve anaerobic conditions without substantialsulfide generation; ii. stopping the mixing for a period of time; iii.mixing; and iv. mixing with aeration to achieve biological growthconditions without substantial production of obligate aerobes.
 35. Themethod of claim 28, wherein controlling the off-line treatment tankcomprises: i. mixing the drawn-off portion of wastewater withoutaeration to achieve anaerobic conditions without substantial sulfidegeneration; ii. mixing with aeration to achieve biological growthconditions without substantial production of obligate aerobes; and iii.stopping the aeration but continuing the mixing.
 36. The method of claim28, wherein controlling the off-line treatment tank comprises: i. mixingthe drawn-off portion of wastewater without aeration to achieveanaerobic conditions without substantial sulfide generation; ii. mixingwith aeration to achieve biological growth conditions withoutsubstantial production of obligate aerobes; iii. stopping the aerationbut continuing the mixing; iv. allowing settling; and v. mixing withaeration to achieve biological growth conditions without substantialproduction of obligate aerobes.
 37. A method of treating wastewater, themethod comprising the steps of: combining wastewater and a firstbiological population having a first-biological population profile in atreatment vessel; exposing the wastewater and first biologicalpopulation in the treatment vessel to at least one of an anaerobic,anoxic and aerobic conditions to form a mixture including sludge;separating the sludge from the mixture; drawing off a first portion ofthe separated sludge and returning said first portion to the treatmentvessel; drawing off a second portion of the separated sludge to anoff-line treatment tank; controlling the off-line treatment tank so asto produce, in the off-line treatment tank, a second biologicalpopulation having a second-biological population profile different fromthe first-biological population profile, such that the second-biologicalpopulation profile is customized to minimize the disposal volume ofresidual solids produced by the treatment of the wastewater, whereinsaid controlling step comprises subjecting the contents of the off-linetreatment tank to a selected sequence of at least two conditionsselected from the group consisting of an aerobic condition, an anoxiccondition and an anaerobic condition, wherein the contents of theoff-line treatment tank are maintained at each condition in the sequencefor a corresponding determined length of time; and returning at least afraction of the produced second biological population to the treatmentvessel.
 38. The method of claim 37, wherein the step of returning atleast a fraction of the produced second biological population includesdecanting a percentage of the produced second biological population fromthe off-line treatment tank.
 39. The method of claim 37, wherein thestep of returning at least a fraction of the produced second biologicalpopulation includes removing a percentage of the produced secondbiological population from the off-line treatment tank.
 40. The methodof claim 37, wherein wastewater is combined with the second portion ofseparated sludge in the off-line treatment tank.
 41. The method of claim37, wherein controlling the off-line treatment tank comprises: i. mixingthe second drawn-off portion without aeration to achieve anaerobicconditions without substantial sulfide generation; ii. mixing withaeration to achieve biological growth conditions without substantialproduction of obligate aerobes; and iv. mixing without aeration toachieve anaerobic conditions.
 42. The method of claim 37, whereincontrolling the off-line treatment tank comprises: i. mixing the seconddrawn-off portion without aeration to achieve anaerobic conditionswithout substantial sulfide generation; ii. mixing with aeration toachieve biological growth conditions without substantial production ofobligate aerobes; iii. mixing without aeration to achieve anaerobicconditions; iv. allowing settling to produce a decantable volume; and v.mixing with aeration to achieve biological growth conditions withoutsubstantial production of obligate aerobes.
 43. The method of claim 37,wherein controlling the off-line treatment tank comprises: i. mixing thesecond drawn-off portion without aeration to achieve anaerobicconditions without substantial sulfide generation; ii. stopping themixing for a period of time; iii. mixing; and iv. mixing with aerationto achieve biological growth conditions without substantial productionof obligate aerobes.
 44. The method of claim 37, wherein controlling theoff-line treatment tank comprises: i. mixing the second drawn-offportion of wastewater without aeration to achieve anaerobic conditionswithout substantial sulfide generation; ii. mixing with aeration toachieve biological growth conditions without substantial production ofobligate aerobes; and iii. stopping the aeration but continuing themixing.
 45. The method of claim 37, wherein controlling the off-linetreatment tank comprises: i. mixing the second drawn-off portion ofwastewater without aeration to achieve anaerobic conditions withoutsubstantial sulfide generation; ii. mixing with aeration to achievebiological growth conditions without substantial production of obligateaerobes; iii. stopping the aeration but continuing the mixing; iv.allowing settling; and v. mixing with aeration to achieve biologicalgrowth conditions without substantial production of obligate aerobes.